In a mobile communication system defined by the 3GPP, each mobile station UE (USIM: User Subscriber Identity Module) possesses at least one of ACs (Access Classes) 0 to 9.
Furthermore, a special mobile station UE (USIM) for network operators, police, or government officials may possess ACs 11 to 15. ACs 11 to 15 are hereinafter called “Special ACs”. Note that AC 10, which is an emergency call AC, is used for issuing a call such as 110 (police) and 119 (fire station), and is not possessed by the mobile station UE (USIM).
FIG. 9 shows an example of an access barring control method according to an Rel. 8 LTE (Long Term Evolution) scheme.
As shown in FIG. 9, according to the Rel. 8 LTE scheme, a mobile station UE is configured to determine whether or not it is possible to issue a call depending on the type of the call, including an mobile terminating call, an emergency call, an mobile originating call, and a mobile originating signaling, and also depending on the barring information (ac-BarringInformation) included in the ACs to which the mobile station UE belongs and the broadcast information (SIB2: System Information Block 2), that is, the “Common AC barring information”.
For example, as regard to an mobile originating call, first of all, the mobile station UE checks whether or not ACs 11 to 15 are possessed, and if ACs 11 to 15 are possessed, the mobile station UE checks the barring information (ac-BarringForSpecialAC) for the “Special ACs” included in the broadcast information (SIB2).
“ac-BarringForSpecialAC” includes one-bit information for each of ACs 11 to 15 (total five bits) expressing whether it is possible to issue a call. When the mobile station UE determines that it is possible to issue a call based on “ac-BarringForSpecialAC” even for any one of ACs 11 to 15 that the mobile station UE possesses, a call request process is started.
On the other hand, when the mobile station UE does not possess ACs 11 to 15, or when it is determined that all of the ACs 11 to 15 possessed by the mobile station UE are not capable of issuing a call based on “ac-BarringForSpecialAC”, the mobile station UE generates a uniform random number between 0 and 1, and determines whether or not the generated random number is smaller than the “ac-BarringFactor” included in the broadcast information (SIB2).
If the generated random number is smaller than “ac-BarringFactor”, the mobile station UE activates the call request process, but in other cases, the mobile station UE activates a prohibition timer for an mobile originating call. When the prohibition timer for an mobile originating call is being activated, the mobile station UE is prohibited from starting the call request process for new mobile originating calls.
Furthermore, the mobile station UE is configured such that when it is attempted to issue a call but this attempt is Rejected by the radio base station eNB, mobile originating calls other than emergency calls are barred for the period of the timer value (that is, during the period the timer T302 is activated) included in RRCConnectionReject.
On the other hand, according to an Rel. 9 LTE scheme, SSAC (Service Specific Access Control) is under discussion. According to SSAC, it is assumed that barring control can be independently enabled in “MMTEL/IMS-voice mobile originating calls”, “MMTEL/IMS-video mobile originating calls”, and “other mobile originating calls”.
Thus, according to the Rel. 9 LTE scheme, the three types of barring information such as “ac-BarringFactor”, “ac-BarringTime”, and “ac-BarringForSpecialAC” are expected to be broadcast independently.
Note that new barring information (“SSAC barring information”) is expected to be broadcast for “MMTEL/IMS-voice mobile originating calls” and “MMTEL/IMS-video mobile originating calls”, and the “Common AC barring information” that is used in the Rel. 8 LTE scheme is expected to be applied as barring information for “other mobile originating calls”.
Here, identification of the type of an mobile originating call in an AS layer function is not desired when protocol separation is taken into consideration, and therefore, barring (SSAC barring) of “MMTEL/IMS-voice mobile originating calls” and “MMTEL/IMS-video mobile originating calls” is expected to be achieved in an MMTEL/IMS layer function.
However, in a mobile communication system according to the Rel. 9 LTE scheme that is assumed as described above, there occurs a need of notifying the MMTEL/IMS layer function of the ACs to which the mobile station UE belongs, from the AS layer function.
In this case, in a terminal such as a data card, the MMTEL/IMS layer function may be installed on the laptop side, and there is a possibility that the ACs of the mobile station UE are exposed from the terminal to the laptop or the user, resulting in a problem because it is not desirable in view of security.